Video graphics array (VGA) is a graphics display system for personal computers (PCs). VGA has become one of the defacto standards for PCs, providing a resolution of 720 by 400 pixels in text mode and a choice of resolutions in graphics mode (e.g., 640 by 480 by 16 colors, 320 by 200 by 256 colors). VGA is a hardware specific standard that employs analog signals, not digital signals. Other standards have appeared since the 1987 VGA debut but VGA remains the lowest common denominator standard and thus substantially all PCs support VGA. However, VGA has drawbacks.
For example, VGA is hardware specific and thus to program to VGA requires knowledge of hardware, software, and assembly and/or machine language, which makes such programming difficult. Furthermore, some of the original requirements of VGA are becoming harder to support as the PC continues to evolve, requiring extensive rework of assembler and/or machine coded BIOS (Basic Input Output System) code to support enhancements. The VGA standard from the 1980s makes demands on hardware and software that are outdated today, such as the use of Int 10 services, a non-linear frame buffer, a limited range of display modes, and direct register addressing using real-mode assembly language. Further limitations include that BIOS code executes in a real-mode x86 environment and that the video BIOS image is restricted to an absolute maximum of 64K. Additionally, VGA is tied to legacy I/O (Input/Output) and memory usage that has a non-relocateable memory and a non-intuitive, non-linear frame buffer layout. Also, VGA has limited mode support (e.g., 80×25×70 Hz characters and 640×480×16-color graphics). VGA also does not support power management, which has become increasingly important in mobile computing environments. Also, there is no firmware support of VGA adapters in a multiple-monitor configuration under existing operating systems.
Substantially all display devices support VGA in addition to the high-performance device capabilities they expose. Many PCs require a VGA device to be in the machine before the system can boot and BIOS Power-On Self Test (POST) messages require a VGA device for display. In addition to being a defacto universal standard, VGA is also now a dated standard, with capabilities that have not changed significantly as the PC platform has evolved.